Endocrine disruptors which disrupt the endocrine system in a living body have been understood to be a serious social problem since T. Colborn published “Our Stolen Future” in 1996. The endocrine system in a body is a system which maintains and regulates generation of an organism, development of sexual organs, and functions of various organs in a living body caused by actions of an androgen, an estrogen, a thyroid hormone, an adrenal cortical hormone, and the like. Endocrine-disrupting chemicals are a group of substances which disrupt the endocrine system in a body. A large amount of endocrine disruptors are discharged into the world of nature by various human activities and the like and cause a great deal of abnormal growth in wildlife.
Along with estrogenic substances, organochlorine compounds such as pesticides, antibacterial agents, and herbicides and industrial chemicals such as bisphenol A and nonylphenol are known as endocrine-disrupting chemicals. Among these, the use of industrial chemicals has been strictly regulated by The Water Pollution Control Law and other pollution regulations because of their toxic property. The amount of these chemicals discharged into the environment is now decreasing. However, the amount of estrogenic substances such as 17β-estradiol, estrone, and estriol contained in human and animal urine discharged into the environment is increasing along with the population growth. Abnormal feminization of wildlife has been confirmed in rivers and lakes into which large amounts of domestic wastewaters flow from urban area (“The Feminization of Nature” written by Deborah Cadbury, edited by Taisen Iguchi, Shueisha, 1998). This suggests that incapacity to fertilize may unbalance ecosystems.
17β-estradiol shown by the following formula (I) is a steroid hormone secreted from the ovarian follicle and is the most physiologically active substance among the estrogenic substances. Its secretion is controlled by follicle-stimulating hormones and luteinizing hormones in the pituitary gland. 17β-estradiol is used as a medicine for treating amenorrhea, menstrual disorder, dysmenorrhea, hypoplasia uteri, postmenopausal syndrome, and the like.

Estrone shown by the following formula (II) is a type of estrogen which is a metabolite of 17β-estradiol. Estrone which has a strong estrogenic activity appears in urine and is discharged from the body. Estrone is used as a hormonal agent for treating sexual dysfunction in women, postmenopausal syndrome, prostate cancer in men, and the like.

Estriol shown by the following formula (III) is an estrogen which is a metabolite of 17β-estradiol in a body which is formed through estrone and discharged in the urine. Estriol has an estrus effect.

As described above, estrogenic substances are used as human medications. They are contained in the urine and discharged from the body together with the urine. These substances are also administered to farm animals and are thus discharged into the environment from livestock farms. Because wildlife and fishes in rivers and lakes are contaminated with these estrogenic substances, it is necessary to decrease the estrogenic substances contained in wastewater before discharge into a river or the like, for example, in wastewater treatment facilities.
There are three types of wastewater treating methods currently used in wastewater treatment facilities: physical treatment, chemical treatment, and biological treatment. The physical treatment includes centrifugation, filtration, pressurized flotation separation, adsorption, and the like. Chemical treatment, specifically, is detoxification of toxic substances by adding chemicals and the like, electrodialysis, ion exchange, and the like. On the other hand, biological treatment is a treatment using microorganisms to degrade and remove organic substances in wastewater and is effective for treating substances difficult to treat physically or chemically.
Biological treatment has been popularly used in many wastewater treatment facilities in recent years. Biological treatment, in general, has three steps: a preliminary treatment, a biological oxidation treatment, and a sludge treatment. The preliminary treatment comprises treatments using a screen, a sand basin, a settling basin, a floating bath, and the like. These devices remove solid materials and inorganic floating materials having a large particles size in wastewater, and are useful in reducing the load of organic substances in biological oxidation treatment facilities.
Biological oxidation treatment, on the other hand, uses microorganisms. As the method of using microorganisms, a method of causing microorganisms to adhere to the surface of a solid support and growing the microorganisms on the surface, and a method of suspending microbial groups in a liquid can be given. The former method is usually carried out using a fixed bed apparatus of a trickling filter process, while a fluidized bed apparatus of an activated sludge process is used for the latter method.
Among these, in the method of treating wastewater using a fixed bed apparatus, a bonding immobilization method, an enclosing immobilization method, and the like are employed to immobilize microorganisms. The bonding immobilization method is a method of causing microorganisms to adhere to an insoluble carrier by a covalent bond, ionic bond, hydrogen bond, physical adsorption, or the like. The enclosing immobilization method is a method of enclosing the microorganisms in a polymer gel produced by polymerization or association of a low molecular compound or by changing the state of a polymer compound from a soluble state to an insoluble state. A ceramic carrier, a cellulose carrier, particulate activated carbon, and the like are used as a material in the former method, while polyvinyl alcohol (PVA), carageenan, and the like are used as a material in the latter method.
Since the activated sludge treatment, trickling filter treatment, and the like are very excellent methods of reducing pollution substances in wastewater, various biological approaches of degrading endocrine disruptors has been actively undertaken in recent years. Some efforts include improvement of the treating efficiency and employment of a more stringent standard for screening and selecting microorganisms that can degrade endocrine disruptors of which the treatment is difficult. Until now, microorganisms belonging to the genus Sphingomonas capable of degrading nonylphenol (Patent document 1), microorganisms belonging to the genus Fusarium capable of degrading dioxine (Patent document 2), microorganisms belonging to the genus Fusarium capable of degrading ethynylestradiol which is a synthetic estrogen (Patent document 3), and the like have been reported. The applicant of the present invention has reported microorganisms belonging to the genus Rhodococcus or Sphingomonas which can degrade 17β-estradiol and the like (Patent document 4).
However, few microorganisms capable of quickly and effectively degrading estrogenic substances which are particularly difficult to degrade by treatment with microorganisms have been discovered. A microorganism having higher degrading capability is demanded.
The applicant of the present invention has reported microorganisms belonging to the genus Rhodococcus or Sphingomonas which can degrade 17β-estradiol and the like. However, although these estrogen degrading bacteria exhibit good degrading capabilities in circumstances in which a comparatively low-concentration estrogen continuously flows, their effects are not sufficient in circumstances that allows a high-concentration estrogen to primarily flow.    [Patent document 1] Japanese Patent Application Laid-open No. 2001-333767    [Patent document 2] Japanese Patent Application Laid-open No. 11-341978    [Patent document 3] Japanese Patent Application Laid-open No. 2003-52356    [Patent document 4] Japanese Patent Application Laid-open No. 2004-65008